Control your holiday lights with a magic wand

A magnet waved past a Hall-effect sensor does the trick.

Vladimir Rentyuk, Zaporozhye, Ukraine; Edited by Paul Rako and Fran Granville -- EDN, December 16, 2011

This circuit allows you to turn on your holiday bulbs with a wave of the magic wand. The strings flash in sequence. At the heart of the idea is the magnetic wand. It gives the appearance of real magic. The main part of the circuit is a digital magnito-resistive sensor IC₄ (Figure 1). Typical Hall-effect sensors are not suitable for this design because they do not work over an extended sensing distance. They also do not switch when excited by either magnetic pole. The Honeywell 2SS52 sensor works from either the north or south pole. It has good sensitivity to a magnetic field.


When you move a magic wand near sensor IC₄, the trigger IC_2-1 will change its output. This enables the signal generator and a binary counter formed by IC_2-2, IC_3-1, and IC_3-2. The output drivers Q₁, Q₂, and Q₃ will be opened by high outputs of the binary counter. The LED’s chains will sequence in a binary counting mode. You can adjust the counting frequency by changing the values of R₄ and C₃. A second swipe of your magic wand will toggle IC₄ and the lights will turn off. You could adapt this circuit with optocouplers and ac TRIACs to drive LED lights meant for ac wall power.